The Parotid Region of the Face

The parotid region is actually
part of the neck but it extends into the facial region as well. It also
must be studied before the infratemporal region can be examined. We will
examine the parotid region from superficial to deep pointing out the gland
itself and the structures running through it.

The parotid gland is a superficial structure
located in the upper neck above the posterior belly of the digastric muscle.
It is a salivary gland that has a large duct (pd) which crosses the
masseter muscle to pierce the buccinator muscle opposite the upper 2nd
molar tooth. The duct can frequently be rolled between the finger and the
masseter muscle. The skin overlying the lower pole of the gland is supplied
by the greater auricular nerve (ga), a branch of the cervical plexus. You
have already identified the branches of the facial nerve appearing at the
upper and anterior edges of the gland (yellow).

If the parotid gland is carefully removed,
you can identify the structures located within it. The first plane is the
venous plane and consists of the retromandibular vein (rm) and its tributaries
and branches:

st--superficial temporal

rm--retromandibular vein

m--maxillary vein

ad--anterior division

f--facial

cf--common facial

pd--posterior division

pa--posterior auricular

ej--external jugular

The common facial vein empties into the internal
jugular vein and the external jugular into the subclavian vein near its
junction with the internal jugular.

When the venous plane is removed we reach
the important nervous plane. The importance of this plane is the presence
of the facial (VII) nerve. The facial nerve leaves the skull through the
stylomastoid foramen and immediately enters the deep part of the parotid
gland where it gives off its branches:

posterior auricular (pa)

motor branch to posterior belly of digastric
(db)

temporal branch (t)

zygomatic branch (z)

buccal branches (b)

mandibular branch (m)

cervical branch (c)

Deep to the nerves lies the arterial plane
which includes terminal parts of the external carotid artery and
its branches:

external carotid artery (EC)

occipital artery (oc)

maxillary artery (m)

transverse facial artery (tf)

superficial temporal artery

The deepest part of the parotid region
is the parotid bed and houses the deep part of the gland which fills the
small space between the neck of the condyle of the mandible (nc) and the
mastoid process (m). Other structures forming the floor of this space are
the :

styloid process (sp)

stylohyoid muscle (sh)

stylopharyngeus muscle (sph)

posterior belly of the digastric muscle (pbd)

The gland becomes infected and swollen in
mumps. If you have had the mumps, you will realize just how difficult it
is to open your mouth. Now, you can see why this is so. When you open the
mouth, you narrow the parotid bed space and compress the deep parotid gland
between the neck of the condyle and the mastoid process.

The Infratemporal Fossa and Muscles of Mastication

The infratemporal fossa is a small
space between the ramus of the mandible and the lateral pterygoid plate
of the sphenoid. On a skull, it is big enough for maybe 1 1/2 fingers but
it has many things in it. Following is a tabulation of the infratemporal
fossa and all of its contents.

The lateral wall of the infratemporal fossa is noted in the 1st image and consists of the

There are four muscles of mastication on each side that control the movement of the mandible:

masseter

medial pterygoid

lateral pterygoid

temporalis

The lateral pterygoid is the main muscle that opens the mouth. It is helped from gravity and a couple of neck muscles.
It opens the jaw by pulling forward on the neck of the mandible and causing the jaw to drop.

The artery entering the infratemporal
fossa is the maxillary branch of the external carotid artery. As can be
seen, it has many branches (11 in all). You will probably not be responsible
for all of them but I have included them all for completeness.

Maxillary artery

deep auricular (da)

anterior tympanic (at)

middle meningeal (mm)

accessory middle meningeal (amm)

inferior alveolar (ia)

buccal (b)

deep temporal (dt)

posterior superior alveolar (psa)

descending palatine (dp)

infraorbital (io)

sphenopalatine (sp)

External carotid artery (ec)

occipital (oc)

transverse facial (tf)

superficial temporal (st)

The sphenopalatine and descending palatine
arteries pass through a small space between the pterygoid process of the
sphenoid and the maxilla, the pterygomaxillary fissure.

The mandibular nerve (V3) is the nerve
of the infratemporal fossa and is responsible for supplying the muscles
of mastication plus two tensor muscles: 1) tensor palati and 2) tensor
tympani. The branches are as follows:

deep temporal (dt)

auriculotemporal (at)

inferior alveolar (ia)

nerve to the mylohyoid (nmh)

lingual (l)

buccal (b)

branches to lateral pterygoid (not labeled)

Not shown:

meningeal branch

nerve to masseter

The Temporomandibular Joint (TMJ)

The temporomandibular joint (tmj) is a
synovial type joint separated by an interarticular disc. The disc splits
the joint into two separate joints. The upper joint (ujc) is between the
mandibular (articular) fossa of the temporal bone and the articular disk
and provides a sliding motion when the lateral pterygoid contracts and
pulls the condyle and disc forward.

The lower joint (ljc) is between the articular
disc and the head of the condyle of the mandible. The action here is a
hinge-like action, in which the mandible drops, thereby opening the mouth.

When dentition or muscle action is not in proper alignment, the joint can be secondarily affected and pain can ensue. This is TMJ disease and requires dental specialists to correct the
problem.